Selective fire converter for semiautomatic firearms



Aug. 18, 1953 A. F. GAIDOS SELECTIVE FIRE CONVERTER FOR SEMIAUTOMATIC FIREARMS 4 Sheets-Sheet 1 Filed Jan. 16, 1950 INVENTQR. AMA/20 E 639/005.

Aug. 18, 1953 A. F. GAlDOS SELECTIVE FIRE CONVERTER FoR SEMIAUTOMATIC FIREARMS 4 Sheets-Sheet 2 Filed Jan. 16, 1950 INVENTOR. A4 o/vzo E 60/005.

ATTOR Aug. 18, 1953 A. F. GAIDOS SELECTIVE FIRE CONVERTER FOR SEMIAUTOMATIC FIREARMS 4 Sheets-Sheet 5 Filed Jan. 16, 1950 mm mm mm w. mh J I l l l I l|l Q a 4 Mm Whmmq 0 mm. R I E@ EE- La w w m mm 6 w, kw Mk Aug. 18, 1953 A. F. GAIDOS 2,649,030

SELECTIVE FIRE CONVERTER FOR SEMIAUTOMATIC FIREARMS Filed Jan. 16, 1950 4 Sheets-Sheet 4 INVENTOR. A4o/vz0 F: GA/poa.

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Patented Aug. 18, 1953 UNITED STATES @FFHC SELECTIVE FIRE CONVERTER FOR SEMI- AUTOMATIC FIREARMS 7 Claims.

This invention relates to a selective fire con verter which may be attached to a semi-automatic firearm to provide either semi-automatic firing or full automatic firing at the selection of the marksman.

Large quantities of the U. S. carbine, caliber .30 Ml have been manufactured and are now stored. This weapon, as disclosed in Humeston Patent No. 2,308,283, is designed for semi-automatic operation. That is, a pull on the trigger will fire a single round, reload a shell in the chamber and cock the firing mechanism, but will not fire a second round until the trigger is released and again pulled.

Several attempts have been made to modify the M1, caliber .30 carbine so it will fire automatically as long as the trigger is depressed, or, at the selection of the operator, will fire semi-automatically. Of these conversion efforts, only the selective fire converter disclosed in my copending patent application, Serial No. 780,214., filed October 16, 1947, accomplishes the desired result without modifying or remachining operating parts of the basic weapon. The present invention is an improvement upon the selective fire converter disclosed in that patent application.

A major object of this invention is to provide a selective fire converter of simplified construction which may be attached to a semi-automatic firearm without modifying, replacing, or remachining any operating parts of the firearm.

A particular object of the invention is to provide an efiective converter having few parts, all of which operate upon a bracket which may be attached to one side of the firearm.

Another object of the invention is to provide a selector conveniently located so it may be readily shifted by the thumb of the marksmans right hand.

In accordance with these objects, an important feature of my invention resides in the arrangement of a bracket and housing for supporting the complete converter on one side of the firearm. A selector lever on the bracket may be shifted by the marksmans thumb to automatic or semiautomatic positions. Another feature resides in the construction of an actuator bar having spaced abutments, one of which is adjustable longitudinally of the bar, to be engaged by the reciprocating slide on the firearm and thereby reciprocate the actuator bar. Still another feature resides in the provision of a pivoted end piece slidably mounted on the bracket and engageable by one end of the actuator bar, which end piece is shiftable between operative and inoperative positions by movement oi the selector.

Other objects and advantages of the invention will become apparent from the following specification taken in conjunction with the accompanying drawings wherein:

Figure 1 is a partial side elevational view with some parts broken away and others in section, of the receiver and trigger housing of a semi-automatic firearm to which the present invention may be attached;

Fig. 2 is a similar view of a semi-automatic firearm to which is attached a selective fire converter embodying the invention in its preferred form;

Fig. 3 is a partial elevation of the firearm and converter shown in Fig. 2, as seen from the opposite side, some parts being broken away and others shown in section for purposes of clearness, the selector being shown in automatic position with the hammer cocked;

Fig. 4 is a view of the firing mechanism similar to Fig. 3, with the trigger pulled and the hammer moved to its fired position;

Fig. 5 is a view similar to Fig. 3, after the firearm is fired and showing the bolt and slide in recoil position and the trigger retained in its pulled position;

Fig. 6 is a view similar to Fig. 5, with the bolt and slide returned almost to battery position;

Fig. '7 is a view similar to Fig. 6', with the bolt and slide completely returned to battery position, and the hammer released to firing position;

Fig. 8 is a partial view showing the parts positioned similar to Fig. 3, but with the selector in semi-automatic position;

Fig. 9 is a perspective view of the bracket and associated parts of the selective fire converter embodying the invention in its preferred form, the housing being removed;

- Fig. 10' is a perspective view of the housing forming a part of the selective fire converter;

Fig. 11 is a perspective view of the actuator bar forming a part of the invention;

Fig. 12 is a side elevation of the selective fire converter with the housing removed;

Fig. 13 is an end view of the bracket and associated parts as seen from the rear or right side of Fig. 12;

Figure 14 is a perspective view of the selector cam and its operating lever; and

Figure 15 is a horizontal sectional view of the front end portion of the actuator bar.

In its preferred form. the invention includes a bracket secured by the hammer pin to one side of the firearm. Pivoted on the bracket is a sear tripper movable from inoperative to operative position by the trigger and normally urged toward inoperative position by a spring. Slidable relative to the bracket is an actuator bar having spaced abutments on its forward portion to engage and be reciprocated by the automatically reciprocated slide on the firearm. Adjustment of the forward abutment produces the desired reciprocation of the actuator bar which is guided by the housing (Fig.

Supported on the bracket and secured by the transverse receiver screw is a housing having a portion extending forwardly of the bracket to form a guideway in which the actuator bar reciprocates. Pivotally connected to the rear part of the bar is an end piece extending rearwardly of the bracket and having an inwardly extending ear which engages the sear tripper when the latter is moved by the trigger to operative position. On the bracket is a Spring yieldingly urging the ear on the end piece toward the sear tripper so rearward movement of the end piece by the actuator bar causes the end piece to override the sear tripper while forward movement of the end piece moves the sear tripper to depress the sear and release the hammer.

Also, on the bracket is a selector to shift the end piece to a displaced position where it will not engage the sear tripper and the firearm will fire in semi-automatic fashion. This selector is preferably in the form of a cam pivoted on the bracket and shift-able by a selector lever to raise the end piece against the force of the spring acting thereon. Detents in the housing retain the selector lever in either its automatic or its semi-automatic position.

As the selective fire converter of the present invention is particularly adapted for attachment to the U. S. carbine, caliber .30 M1, the operating parts oi this basic weapon are illustrated in Fig. 1. This carbine includes a receiver 2! to which is attached, by a transverse receiver pin 22, a trigger housing indicated generally at '23. Slidable along track 24 beneath barrel 2 i is an automatically reciprocated slide 25 which is moved rearwardly by piston 23 which is operated by explosion gases from barrel 2| each time the weapon is fired. Slide 25 is thus moved rearwardly against the action of slide spring 2? 'until rear end 28 of the slide comes to rest on abutment 29 on the receiver 2!. Then, spring 2'! returns the slide 25 to its forward position. Bolt 3! is operated by the slide to cook hammer 32 automatically each time the gun is fired. Hammer 32 is pivoted on hammer pin 30 and is provided with a conventional hammer notch 33 which may be engaged by sear 34- to retain the hammer in cocked position. The hammer is urged toward firing position by hammer spring 35.

Sear 34 is provided with a transverse slot enabling the sear to float back and forth on sear pin 3'1! which extends between upwardly projecting ears 38, 38, on trigger 35. Pin 3? also serves as the pivot pin for the trigger 39. A sear spring 4! is interposed between the body of the trigger 39 and sear 34 to normally force the sear 34 forwardly with respect to sear pin 31, so rear portion 42 of sear 34 is normally disposed forwardly of upwardly projecting lip 43 on the trigger. A conventional trigger spring 44 normally urges trigger 33 toward its forward position. When bolt 3| is moved rearwardly by slide 25, it turns hammer 32 in a clockwise direction as viewed in Fig. 1 until nose 45 on the sear 34 engages hammer notch 33. Then, when bolt 3! turns to battery position, hammer spring 35 causes hammer 32 to shift sear 34 rearwardly with respect to sear pin 3'! so rear portion 42 of the sear 34 is disposed above upwardly projecting lip 43 on the trigger 39. The mechanism is retained in this position until the trigger is pulled thereby raising lip 43 to move the sear in a counter-clockwise direction, as seen in Fig. l, and releasing the sear from the hammer notch 33 so the hammer 32 is moved by spring 35 to fire the weapon. Following this, slide 25 moves bolt 3! to recock the hammer 32. Assuming the trigger 33 is held in its pulled position, sear 34 will be moved by sear spring 4! forwardly with respect to sear pin 31. Then, when hammer notch 33 engages the nose 45 of sear 34, and bolt 3! returns to ba tery position, hammer spring 35 will shift the hammer and sear until rear portion 42 of the sear 34 engages upwardly projecting lip 43 on the trigger. Thus, even though the trigger is pulled, the gun will not again fire. To fire it. it is necessary that the trigger first be released permitting the sear 34 to move rearwardly until its rear portion 42 is positioned above lip 43 on the trigger 39. Then, when the trigger is again pulled the sear will be disengaged from the hammer notch and the cycle repeated.

This basic weapon is of the semi-automatic type because it automatically cocks the hammer and loads a shell into the chamber each time the slide 25 is operated as a result of the gun being fired. However, the sear and trigger mechanism is so designed that the trigger must be released and again pulled before the gun will fire a second time.

According to the present invention, a selective fire converter may be easily attached to this basic weapon so it may be fired semi-automatically as already described, or automatically as long as the trigger remains pulled.

In Fig. 2, there is illustrated the same basic weapon shown in Fig. 1 with a selective fire converter embodying the present invention attached thereto. This selective fire converter has a bracket 5| which is in the form of a plate of substantially rectangular shape. This bracket 5! is secured onto the trigger housing adjacent the sear and hammer by a bolt 30 which is substituted for the hammer pin at of the basic weapon. To properly aline the bracket with respect to the trigger housing, an elongated sear pin 3'! is substituted for sear pin 3'! and extends beyond one side of the trigger housing through an aperture in the bracket 5 i. A pin 50 mounted on the inner side of bracket 5! serves as a pivot for sear tripper 52 which is thereby pivoted above sear 34 and trigger 39. Extending downwardly from the rear arm of the sear tripper 34 is a trigger engaging foot 53 slightly offset inwardly so it will engage and normally rest upon upwardly extending lip 43 on the trigger 39. Extending upwardly on this rear arm of the sear tripper 52 opposite the trigger engaging foot 53 is an actuating projection 54. Forwardly of pivot pin 50 and preferably as an integral part of sear tripper 52 is a downwardl extending sear engaging nose 55 slightly offset inwardly to a position above the sear 34 so it will engage and depress sear nose 45 upon being turned in a counter-clockwise direction as viewed in Fig. 2.

A tension spring 56 is coiled about pivot pin 50 and has one end 51 engaging the sear tripper 52 tending to turn the sear tripper 52 in a clockwise direction, as viewed in Fig. 2, so trigger engaging foot 53 is yieldingly urged downwardly upon upwardly extending lip .43 on the trigger 39.

Enclosing a part of the bracket 5! is a housing 58 secured alongside the trigger housing by hammer bolt 30. This housing 58 has a forwardly extending portion 59 retained in position by a transverse receiver bolt 22 substituted for the pin 22. An upper part 6! of forward portion 59 is shaped to form a guideway so an actuator bar 62 may slide relative to the firearm and selective fire converter bracket 5| in the guideway between the side of receiver 2| and the guideway 6| on the housing. At the rear end of actuator bar 52 is a hole 63 engaging an inwardly projecting pin 63 extending through a longitudinally elongated slot 64 (Fig. 9) formed in the upper portion of bracket 5!. Preferably, the pin has a loose fit with respect to actuator bar 62 so the pin 53 may pivot with respect to the bar. It will be apparent that pin 63 sliding back and forth in slot 64 provides a guide for reciprocation of the actuator bar 52 with respect to bracket 5!. Pivotally connected to the rear end of actuator bar 52, which is slidably mounted on bracket 5| by pin 63 passing through slot 54, is an end piece 55 which extends rearwardly from the actuator bar 62 between the bracket 5| and its associated housing 58. End piece 65 has an inwardly projecting ear 66 arranged to overlie and/or engage actuating projection 54 on the sear tripper 52. A tension spring 61, which may be a continuation of the spring 56, is held on the bracket 51 by stud 68 and engages the upper side of ear 65 to yieldingly urge the car 56 downwardly. toward sear tripper 52. Also, pivoted on the bracket 5|, as by pin 69, is a selector cam H having a cam surface 12 (Fig. 14) formed by bending the strip material of the cam. Extending upwardly from the cam H is a selector lever '13. The cam H has its cam surface so arranged that end piece 65 may be raised or lowered by shifting the position of lever '13.

. As illustrated in Fig. 2, selector lever 13 is in semi-automatic position. In this position, cam surface 12 turns end piece 55 about its pivot 63 thereby raising ear 56 to a position displaced above actuating projection 54 on sear tripper 52. To retain the selector lever 13 in semi-automatic position, housing 58 is formed with a notch 15 in its rim '16 (Fig. 10). This provides a detent to retain the selector lever in its semi-automatic position. Movement of selector lever 13 from the position shown in Fig. 2 forwardly or counter-clockwise, as viewed in Fig. 2, to a position as shown in Fig. 3 will move cam surface 12 downwardly permitting spring Bl to move ear S6 downwardly so end piece 65 is turned about its pivot from the raised position shown in Fig. 2 to an operative position as shown in Fig. 3. A notch i? in rim 75 on the housing 58 provides a detent retaining the selector lever 13 in its forward or automatic position.

At the forward portion of actuator bar 62 there are provided spaced abutments BI and 82 arranged to be respectively engaged by the forward and rearward ends of slide 25 upon reciprooation of the slide. Thus, when the gun is fired, slide 25 moves rearwardly until it engages rear abutment 82 of the actuator bar 52, then actuator bar 62 is moved rearwardly until abutment 29 on the receiver arrests movement of the slide 25. During forward movement of the slide 25 under the force of spring 21, its forward end engages abutment 8i and moves the actuator bar 52 forwardly until forward movement of the slide 25 is arrested by piston 25. Preferably, intermediate abutment 82 on the actuator bar 62 is formed as a bend in the bar. Forward abutment 8| preferably is a block having a serrated surface 84 (Fig. 15) engaging a correspondingly serrated surface on the forward end of actuating bar 52. Abutment 8| may have an elongated slot 86 through which extends a bolt 81 threaded into the actuator bar 62. Once the abutment BI is adjusted to its proper position, bolt 81 may be tightened to securely retain the abutment on the end of the bar. The abutments 8| and 82 are so spaced and arranged with respect to the slide 25 and its path of reciprocation that actuator bar 62 is automatically reciprocated a distance shorter than the length of slot 64 in the bracket 5 I.

In operation, with the selector lever 13 in its automatic position and the hammer cocked as shown in Fig. 3, the marksman pulls trigger 39 so its lip 43 raises rear portion 42 of scar 34, thereby removing sear nose 45 from hammer notch 33 and permitting hammer spring 35 to move the hammer forwardly and fire the gun. Pulling the trigger 39 also causes lip 43 to engage and raise trigger engaging foot 53 to turn sear tripper 52 clockwise, as viewed in Fig. 3, so actuating projection 54 is raised from its inoperative position, as shown in Fig. 3, to its operative position, as shown in Fig. 4. It will be noted that after the gun is fired, as shown in Fig. 4, sear 34 moves forwardly under the action of sear spring M. After the gun is fired, explosion gases act on piston 25 to reciprocate slide 25 rearwardly. This rear motion of slide 25 first causes bolt 3! to turn the hammer 32 to a position as shown in Fig. 5, which is actually turned counter-clockwise beyond it cocked position, as illustrated in Fig. 3. When the slide engages intermediate abutment 82 on the actuator bar 62, it reciprocates actuator bar 52 rearwardly in guideway 6| so pin 63 is moved rearwardly in slot 65 and end piece 55 is moved rearwardly. Inasmuch as actuating projection 54 on the sear tripper 52 is raised to operative position, and ear 66 is lowered to its automatic position, the car 66 will engage the actuating projection 54. As the actuator bar 62 continues to move rearwardly, ear 66 will override the upwardly sloping surface of actuating projection 54 and will thereby be raised against the action of spring 61. Continued rearward movement of slide 25 will move the actuator bar 62 a sufficient distance that ear 66 on end piece 35 will drop behind actuating projection 54 to a position as shown in Fig. 5. As slide 25 moves forwardly, bolt 3| moves away from hammer 32 so the hammer may turn clockwise as viewed in Fig. 5. Provided trigger 39 remains pulled, hammer spring 35 will cause the hammer 32 to move sear 3t rearwardly on sear pin 3'! until rear part 42 of the sear 34 engages lip 43 on the trigger 39. Then the hammer will be retained in cocked position. With the slide 25 in the position shown in Fig. 6, the bolt has been returned to battery position and a new shell has been inserted in the chamber as described in the above-mentioned Humeston patent. As the slide 25 continues to move forwardly from the position shown in Fig. 6, it engages forward abutment SI and reciprocates actuator bar 52 with its end piece 65 forwardly so ear 66 engages behind actuating projection 54 and turns sear tripper 52 clockwise, as viewed in Fig. '7. When the sear tripper 52 is thus turned, its sear engaging nose 55 depresses sear nose 45 to release the hammer to again fire the weapon. It will be noted that the sear tripper is not actuated to release the hammer until the bolt has'returned to battery position; However, immediately thereafter, slide 25 reciprocates actuator bar 62 forwardly to repeat the firing cycle. In this way, the weapon will automatically fire as long as the trigger 39 is pulled. When the trigger is released, sear tripper 52 is turned counter clockwise by spring 56 to the position shown in Fig. 3 where actuating projection 54 is in its inoperative position so it will not be engaged by ear 66 and firing of the weapon will cease.

With the selector lever in its forward position as just described, the weapon is fired automatically as long as the trigger is pulled. To convert from automatic to semi-automatic fire, it is only necessary for the marksman to move with the thumb of his right hand, the selector lever 13 rearwardly from the position shown in Fig. 7 to the position shown in Fig. 8. As illustrated in Fig. 12, with the selector lever 13 forward in its automatic position as illustrated in full lines, end piece '65 and its ear 56 are lowered to their operative positions. Movement of selector lever 13 to semi autcmatic position, as shown in dotted lines in Fig. 12, causes cam surface 12 to engage the underside of end piece 65 and turn it counterclockwise as viewed in Fig. 12, thereby raising the end piece and its car 66 to inoperative position, as shown in dotted lines in Fig. 12. In its raised inoperative position, ear 66 cannot engage actuating projection 54 on the sear tripper. Hence, the gun will fire semi-automatically in the same fashion as the basic weapon.

From the foregoing description it will be seen that the selective fire converter is a unitary construction on a bracket with a housing which may be readily attached to the side of the Weapon by a new sear pin 3'1, a hammer bolt 3%) substituted for the hammer pin 30, and a new transverse receiver bolt 32 substituted for the receiver pin 22. To install this converter it is not necessary to replace, or remachine, or in any way alter operating parts of the gun. The converter is attached to the side of the weapon and when attached selectively provides either full automatic or semiautomatic firing of the weapon. It is so simple that it may be attached by a soldier in the field because he need only dismantle the trigger mechanism and re-assemble it with the new sear pin and hammer bolt to attach the selective fire converter alongside the trigger housing. Then, by a manipulation of his right thumb to shift the selector F3 he may fire the gun either automatically or semi-automatically.

What is claimed is:

1. In an automatic firearm having a hammer, a sear for retaining the hammer in cocked position, a trigger for disengaging the sear, and an automatically operated reciprocable slide movable from a battery position to a recoil position to cock the hammer following each discharge; a selective fire converter comprising a bracket on one side of the firearm adjacent the trigger and sear, a sear tripper pivoted on said bracket above the trigger engageable with and movable by the trigger from an inoperative position to an operative position, an actuator bar slidable on said bracket reciprocated by said slide, an end piece pivotally connected to said bar to engage and operate said sear tripper, and a selector cam pivoted on said bracket arranged to engage and shift said end piece to an inoperative position displaced from said sear tripper.

2. In an automatic firearm having a hammer, a sear for retaining the hammer in cocked position, a trigger for disengaging the sear, and an automatically operated reciprocable slide movable from a battery position to a recoil position to cock the hammer following each discharge; a selective fire converter comprising a bracket on one side of the firearm adjacent the trigger and sear, a scar tripper pivoted on said bracket above the trigger engageable with and movable thereby, an actuator bar slidable relative to said bracket, a stud connected to said bar and slidable in a slot formed in said bracket, an end piece pivotally connected to said stud engaging and operating said sear tripper upon reciprocation of said actuator bar, and a selector on said bracket for shifting said end piece relative to said sear tripper.

3. In an automatic firearm having a hammer, a sear for retaining the hammer in cocked position, a trigger for disengaging the sear, and an automatically operated reciprocable slide movable from a battery position to a recoil position to cock the hammer following each discharge; a selective fire converter comprising a bracket on one side of the firearm adjacent the trigger and sear, a sear tripper pivoted on said bracket above the trigger engageable with and movable thereby, an actuator bar slidable relative to said bracket reciprccated by the slide, an end piece pivotally connected to said bar and having an inwardly extending sear tripper engaging projection, a tension spring on said bracket yieldingly urging said projection downwardly toward said sear tripper to operate said tripper upon reciprocation of said bar, and selector means for moving said projection against the action of said spring.

4. In an automatic firearm having a hammer, a sear for retaining the hammer in cocked position, a trigger for disengaging the sear, and an automatically operated reciprocable slide movable from a battery position to a recoil position to cock the hammer following each discharge; a selective fire converter comprising a bracket on one side of the firearm adjacent the trigger and sear, a sear tripper pivoted on said bracket above the trigger engageable with and movable thereby, an actuator bar slidable along said bracket reciprocated by the slide, an end piece pivotally connected to said actuator bar and extending rearwardly of said bracket, a tension spring on said bracket yieldingly urging said end piece toward said sear tripper, and a selector cam pivoted on said bracket engaging said end piece to move it against the force of said spring.

5. In an automatic firearm having a hammer, a scar for retaining the hammer in cocked position, a trigger for disengaging the scar, and an automatically operated reciprocable slide movable from a battery position to a recoil position to cock the hammer following each discharge; a selective fire converter comprising an actuator bar slidable along one side of the firearm, means operated by the slide for reciprocating said bar, a pivotally mounted sear tripper having a sear engaging portion for engaging the sear to disengage it from the hammer, an end piece pivotally connected to said bar, said end piece being shiftable between an operative position for moving said sear tripper upon reciprocation of the slide and an inoperative position displaced from said sear tripper, means normally urging said end piece toward one of said positions, and a selector shiftable between an automatic position and a semi-automatic position, said selector being arranged to move said end piece against the action of said urging means.

6. In an automatic firearm having a hammer,

a sear for retaining the hammer in cocked position, a trigger for engaging the sear, and an automatically operated reciprocable slide movable from a battery position to a recoil position to cock the hammer following each discharge; a selective fire converter comprising a bracket on one side of the firearm adjacent the trigger and sear, an actuator bar slidable along said one side of the firearm, means for reciprocating said bar by reciprocating movements of the slide, a pivotally mounted sear tripper having a sear engaging portion for engaging the sear to release it from the hammer, an end piece pivotally connected to said actuator bar, said end piece being shiftable between an operative position for moving said sear tripper upon reciprocation of the slide and an inoperative position displaced from said sear tripper, means normally urging said end piece toward one of said positions, and a selector movably mounted on said bracket and shiftable between an automatic and a semi-automatic position, said selector being arranged to shift said end piece against the action of said means.

'7. In an automatic firearm having a hammer, a sear for retaining the hammer in cocked position, a trigger for disengaging the sear, and an automatically operated reciprocable slide movable from a battery position to a recoil position to cook the hammer following each discharge; a selective fire converter comprising a bracket on one side of the fire arm adjacent the trigger and sear, a guideway on said bracket extending forwardly thereof toward the slide, an actuator bar reciprocated in said guideway by the slide, a pivotally mounted sear tripper having a sear engaging portion arranged to move the sear and release it from the hammer, an end piece pivotally connected to said bar and arranged to engage and move said sear tripper, said end piece being shiftable between an operative position to engage said sear tripper and an inoperative position displaced from said sear tripper, means normally urging said end piece toward one of said positions, and a selector shiftable between an automatic position and a semi-automatic position, said selector being arranged to move said end piece against the action of said urging means.

ALONZO F. GAIDOS.

References Cited in the file of this patent UNITED STATES PATENTS Number 

